Mashup : Appendix - Mashup Expression Language : Syntax
 
Syntax
 
Simple variables
Fallbacks
Dynamic variables and functions
Operations
Functions
Internationalization functions
Combinations
Ternaries
If statements
Foreach loop statements
Flags
Code samples
The MEL supports all the key syntactic constructions: variables, operations, loop statements, etc.
The language itself is entirely lower case.
The following examples are based on a result feed named persons that has an entry with the following metas:
• name: roger
• age: 42
• ${feeds["person"].metas["name"]}: roger, bruce
Simple variables
A variable represents a specific data item, or value, and acts as a placeholder for that value. When a formula encounters a variable, the formula searches for the value of the variable and uses it in the formula.
The basic syntax is: ${my.variable}
Simple expression examples
Expression
Result
hello ${feeds["person"].metas["name"]}
hello roger
hello ${feeds["person"].metas["unknown_meta"]}
hello
hello \${feeds["person"].metas["name"]}
hello ${feeds["person"].metas["name"]}
Fallbacks
You can declare variable fallbacks using pipes |
• ${my.variable|other.variable}
• ${my.variable|other.variable|last.variable}
• ${my.variable|"hardcoded fallback text"}
Fallback/Advanced expression examples
Expression
Result
hello ${feeds["person"].metas["name"]|"world"}
hello roger
hello ${feeds["person"].metas["unknown_meta"]|"world"}
hello world
hello ${feeds["person"].metas["unknown_meta"]|feeds["person"].metas["name"]|"world"}
hello roger
hello ${feeds["person"].metas["unknown_meta"]|feeds["person"].metas["unknown_meta2"]|"world"}
hello world
hello ${feeds["person"].metas["unknown_meta"]|feeds["person"].metas["unknown_meta2"]}
hello
Dynamic variables and functions
Dynamic variables are variables whose values are determined when the program is run.
• ${i18n["machine_"+robot.id]}
• ${math:${op.sum}(1,1)}
Dynamic expression examples
Expression
Result
${fn:${feeds["person"].metas["name"]}(${feeds["person"].metas["age"]})} = ${fn:roger(42)}
result of the function roger passing the parameter 42
Operations
• Strings: ${my.age == "42"}
• Supported numerical operators: - + * / % == != < > ( ) ^ >= <= Example: ${(2+3)*4} = 20
• Supported string operators: == !=
• Logical operators: ${(2 <= 3 && 42 != 21) || 3 >= 3} where && = and || = OR
• Brackets support:
◦ ${page.params["q"][1]}
◦ ${math:sum(1,1)[0]}
• Concatenation and sum: + is the concatenation operator (as in Java) and also the sum operator for numerical operations.
◦ ${"5" + "6"} --> 11
◦ ${"a" + "b"} --> ab
◦ ${"a" + "5"} --> " (it will be resolved to NaN+5)
◦ ${str:join(","a","5")} --> a5
Operation examples
Expression
Result
i am ${feeds["person"].metas["age"]}
i am 42
i am ${feeds["person"].metas["age"] + 10}
i am 52
i am ${feeds["person"].metas["age"] / 2}
i am 21
i am ${feeds["person"].metas["age"] % 40}
i am 2
i am ${feeds["person"].metas["age"] * 2}
i am 84
i am ${feeds["person"].metas["age"] - 20}
i am 22
i am ${feeds["person"].metas["age"] + 10.0}
i am 52.0
i am ${feeds["person"].metas["age"] / 2.0}
i am 21.0
i am ${feeds["person"].metas["age"] % 40.0}
i am 2.0
i am ${feeds["person"].metas["age"] * 2.0}
i am 84.0
i am ${feeds["person"].metas["age"] - 20.0}
i am 22.0
i am ${feeds["person"].metas["age"] == "42"}
i am true
i am ${feeds["person"].metas["age"] == "24"}
i am
i am ${feeds["person"].metas["age"] != "42"}
i am
i am ${feeds["person"].metas["age"] != "24"}
i am true
i am ${feeds["person"].metas["age"] == "roger"}
i am true
i am ${feeds["person"].metas["age"] == "robert"}
i am
i am ${feeds["person"].metas["age"] != "roger"}
i am
i am ${feeds["person"].metas["age"] != "robert"}
i am true
${feeds["person"].metas["age"][0]}
roger
${feeds["person"].metas["age"][1]}
bruce
${feeds["person"].metas["age"][1][0]}
b
${feeds["person"].metas["age"][1][2]}
u
${"world"[1]}
o
${("hello" + "world")[8]}
l
Logical operation examples
Expression
Result
I am ${Roger && 42}
false
I am ${Roger || 42}
true
I am ${Roger || (42 && Roger)}
false
Functions
MEL Functions are classified by categories under the following namespaces:
• category functions: className, url.
• currency: format.
• date: addDays, addYears, addMilliseconds, addMonths, addMinutes, addHours, addSeconds, addWeeks, now, format, elapsedTime.
• entry: cleanId, previewHtmlUrl, thumbnailUrl, downloadUrl, previewImageUrl.
• list: join, size.
• math: min, atan, max, pow, asin, cos, ceil, sqrt, random, log2, sum, round, divide, multiply, log, subtract, exp, abs, floor, sin, avg, tan, acos.
• number: format.
Note: For number approximation, we use the rounding modes described in https://docs.oracle.com/javase/7/docs/api/java/math/RoundingMode.html
• str (string): replace, lowerCase, abbreviate, upperCase, length, hashCode, split, contains, trim, substr.
• var: get, set.
Note: The fn namespace is used as the standard namespace.
Function calls:
• Simple: ${date:now()}
• With arguments: ${str:substr("toto", 2)}
• With variable arguments: ${math:max(${my.age}, ${your.age})}
Function expression examples
Expression
Result
I am ${math:substr(page.params["name"], 0, 3)}
I am rog
${number:format(0.25, 1, 4, 1, 1, true, "HALF_UP")}
0.3
Internationalization functions
• ${user:locale(MELHttpServletRequest request)} returns the locale used by the current user from the HTTP query.
• ${date:format(MELString date, MELString pattern, MELString locale, MELString timeZone)} returns the date formatted as the output pattern using the specified locale and timezone.
• ${i18n:message(MELHttpServletRequest request, MELType code) translates a string like ${i18n[code]} but using the locale from the HTTP query.
• ${i18n:message(MELHttpServletRequest request, MELType code, MELType[]... parameters) translates a string containing variable parts (specified by {0}, {1}, etc.) which are replaced by the values in parameters.
Sample usage:
${user:locale(request)}
> en
${date:format(${entry.metas['date']}, 'dd/MM/yyyy hh:mm:ss', 'en_EN', 'GMT')
> 10/02/2014 12:30:10
${date:format(${entry.metas['date']}, "MM/dd/yyyy hh:mm:ss", "en_US", "GMT-5")}
> 02/10/2014 07:30:10
In localization file (*.properties):
error.message=Error code: {0}

document.summary=created by {0} on {1} at {2}
In the Mashup Builder:
${i18n:message(request, 'error.message', '404')}
> Error code: 404
${i18n:message(request, 'document.summary', author, date, time)}
> created by John Doe on February 10, 2014 at 10:30am
Combinations
• Operations and functions: ${math:max(${my.age}, ${your.age}) + 10}
Ternaries
• Simple: ?{true?yes:no}
• Advanced: ?{${persons.age}?i am ${persons.age / 2}:age not found}
• Short syntax: ?{true?:no}
• Nested: ?{true?{true?nested yes:nested no}:no}
Ternary expression examples
Expression
Result
?{feeds["person"].metas["name"]?meta exists:meta not found}
meta exists
?{feeds["person"].metas["unknown_meta"]?meta exists:meta not found}
meta not found
?{feeds["person"].metas["age"]?i am feeds["person"].metas["age"]/2:age not found}
i am 21
?{true?yes:no}
yes
?{yes:no}
no
?{true?:no}
-
?{true?{true?nested yes:nested no}:no}
nested yes
?{true?{?nested yes:nested no}:no}
nested no
${if feeds["person"].metas["name"] != "roger"} wrong ${elseif math:sum(1,1) ==3} wrong ${elseif math:sum(1,1) == 2} happy ${else} wrong ${/if}
happy
Special ternary expression examples
Expression
Result
hello ${page.params["name"]}
hello roger
hello ${page.params["unknown_meta"]}
hello
hello ?{page.params["name"]?no otherwise}
hello no otherwise
hello ?{page.params["unknown_meta"]?no otherwise}
-
If statements
The If statement enables you to evaluate a sequence of statements if a condition is true and evaluate a different sequence of statements if it is not true.
• You are ${if page.params["n"] != 42} wrong ${elseif math:sum(1,1) ==3} wrong ${elseif math:sum(1,1) == 2} happy ${else} wrong ${/if}
Foreach loop statements
Foreach loops enable you to evaluate a sequence of statements multiple times.
• ${foreach 1,2,3} ${loop.element}?{$loop.hasNext}?,} ${/foreach} go!
• ${foreach number in 1,2,3} ${number}?{${loop.hasNext}?,} ${/foreach} go!
Loop expression examples
Expression
Result
${foreach page.params["name"]}I am ${loop.element}${/foreach}
I am roger
${foreach "a", "b", "c"}${loop.element}${/foreach}
abc
${foreach 1,2,3}and ${loop.index} ${/foreach}
and 0 and 1 and 2
${foreach 1,2,3}and ${loop.element} ${/foreach}
and 1 and 2 and 3
${foreach number in 1,2,3} and ${number} ${/foreach}
and 1 and 2 and 3
Flags
• !m --> HTML escaping
• !x --> XML escaping. For example: ${entry.metas['text']!+x}
• !u --> URL encoding. This flag is useful to declare URLs.
• !h --> Highlighting (only available for metas). For example: ${entry.metas["title"]!h}
Important: We recommend declaring whether flags must be used or not specifically, with the + and - signs. For example: !+h or !+h-x Without the + and - signs, the default behavior is inverted.
Code samples
The two following code samples using MEL can be pasted in an HTML widget. They both contain typical iteration made with foreach statements.
<h1>Iterate over entries</h1>
<ul>
${foreach hit in feed.entries}
<li>
<h1>${hit.title}</h1>
<a href="${entry:downloadUrl(hit, request, '<Page name>')}">Download</a>
<iframe src="${entry:previewHtmlUrl(hit, request, '<Page name>')}"></iframe>
<img src="${entry:previewImageUrl(hit, request, '<Page name>')}" />
</li>
${/foreach}
</ul>
<h1>Iterate over the author facet</h1>
<ul>
${foreach catElement in feeds[’cloudview’].facets[’author’].leaves}
<li>
<a href="${category:url(catElement, request, feeds[’cloudview’])}"
class="${category:className(catElement)}">
${i18n[catElement]}
</a>
</li>
${/foreach}
</ul>
Note: request refers to the request variable available in any context.